Atmospheric ammonia (NH3) is an alkaline gas and a prominent constituent of the nitrogen cycle that adversely affects ecosystems at higher concentrations. It is a pollutant, which influences all ...three spheres such as haze formation in the atmosphere, soil acidification in the lithosphere, and eutrophication in water bodies. Atmospheric NH3 reacts with sulfur (SOx) and nitrogen (NOx) oxides to form aerosols, which eventually affect human health and climate. Here, we present the seasonal and inter-annual variability of atmospheric NH3 over India in 2008–2016 using the IASI (Infrared Atmospheric Sounding Interferometer) satellite observations. We find that Indo-Gangetic Plains (IGP) is one of the largest and rapidly growing NH3 hotspots of the world, with a growth rate of +1.2% yr−1 in summer (June–August: Kharif season), due to intense agricultural activities and presence of many fertilizer industries there. However, our analyses show insignificant decreasing trends in annual NH3 of about −0.8% yr−1 in all India, about −0.4% yr−1 in IGP, and −1.0% yr−1 in the rest of India. Ammonia is positively correlated with total fertilizer consumption (r = 0.75) and temperature (r = 0.5) since high temperature favors volatilization, and is anti-correlated with total precipitation (r = from −0.2, but −0.8 in the Rabi season: October–February) as wet deposition helps removal of atmospheric NH3. This study, henceforth, suggests the need for better fertilization practices and viable strategies to curb emissions, to alleviate the adverse health effects and negative impacts on the ecosystem in the region. On the other hand, the overall decreasing trend in atmospheric NH3 over India shows the positive actions, and commitment to the national missions and action plans to reduce atmospheric pollution and changes in climate.
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•A detailed analysis of atmospheric NH3 over India using satellite observations•Intense agriculture and numerous fertilizer plants make the Indo-Gangetic Plain (IGP) as one of the largest NH3 hotspots of the world.•There is a decreasing trend in annual atmospheric NH3 over India in accordance with the national missions and action plans.•The IGP still shows an increasing trend in NH3 during the monsoon/Kharif season.
Methane (CH4) is a prominent Greenhouse Gas (GHG) and its global atmospheric concentration has increased significantly since the year 2007. Anthropogenic CH4 emissions are projected to be 9390 ...million metric tonnes by 2020. Here, we present the long–term changes in atmospheric methane over India and suggest possible alternatives to reduce soil emissions from paddy fields. The increase in atmospheric CH4 concentrations from 2009 to 2020 in India is significant, about 0.0765 ppm/decade. The Indo-Gangetic Plains, Peninsular India and Central India show about 0.075, 0.076 and 0.074 ppm/decade, respectively, in 2009–2020. Seasonal variations in CH4 emissions depend mostly on agricultural activities and meteorology, and contribution during the agricultural intensive period of Kharif–Rabi (i.e., June–December) is substantial in this regard. The primary reason for agricultural soil emissions is the application of chemical fertilizers to improve crop yield. However, for rice farming, soil amendments involving stable forms of carbon can reduce GHG emissions and improve soil carbon status. High crop production in pot culture experiment resulted in lower potential yield–scaled GHG emissions in rice with biochar supplement. The human impact of global warming induced by agricultural activities could be reduced by using biochar as a natural solution.
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•Significant increase in methane concentration over India in last decade.•Shifting trends in biogenic sources of methane is observed over India.•Seasonal variation in methane concentration depends on agricultural activity.•Methane emissions from soil is modulated with the application of fertilizers.•Alternative organics like biochar may reduce potential soil emissions in paddy.
A nationwide lockdown was imposed in India from 24 March 2020 to 31 May 2020 to contain the spread of COVID-19. The lockdown has changed the atmospheric pollution across the continents. Here, we ...analyze the changes in two most important air quality related trace gases, nitrogen dioxide (NO
2
) and tropospheric ozone (O
3
) from satellite and surface observations, during the lockdown (April
–
May 2020) and unlock periods (June
–
September 2020) in India, to examine the baseline emissions when anthropogenic sources were significantly reduced. We use the Bayesian statistics to find the changes in these trace gas concentrations in different time periods. There is a strong reduction in NO
2
during the lockdown as public transport and industries were shut during that period. The largest changes are found in IGP (Indo-Gangetic Plain), and industrial and mining areas in Eastern India. The changes are small in the hilly regions, where the concentrations of these trace gases are also very small (0
–
1 × 10
15
molec./cm
2
). In addition, a corresponding increase in the concentrations of tropospheric O
3
is observed during the period. The analyses over cities show that there is a large decrease in NO
2
in Delhi (36%), Bangalore (21%) and Ahmedabad (21%). As the lockdown restrictions were eased during the unlock period, the concentrations of NO
2
gradually increased and ozone deceased in most regions. Therefore, this study suggests that pollution control measures should be prioritized, ensuring strict regulations to control the source of anthropogenic pollutants, particularly from the transport and industrial sectors.
Highlights
• Most cities show a reduction up to 15% of NO
2
during the lockdown
• The unlock periods show again an increase of about 40
–
50% in NO
2
• An increase in tropospheric O
3
is observed together with the decrease in NO
2
•Detailed analysis of HCHO over Indian region for the past two decades.•High concentrations of HCHO in the Indo-Gangetic Plain and eastern India.•Ports, cities and mining regions show increasing ...trends in HCHO.•Analysis for the COVID-19 lockdown period shows significant biogenic sources.
Atmospheric formaldehyde (HCHO) has significant adverse health effects at higher concentrations. It is an unstable and inflammable organic compound, and is an index for atmospheric pollution. Although the ambient HCHO is due to methane oxidation, the localised enhancement in HCHO is mostly from the emissions of non-methane volatile organic compounds (NMVOCs). Therefore, assessment of spatial and temporal changes in NMVOCs are key for monitoring air quality and climate change. Here, we analyze two decades of atmospheric HCHO measurements and investigate the HCHO sources in India using satellite observations in 1997–2020. The measurements show very high HCHO concentrations in the Indo-Gangetic Plain (IGP), and south and east India, about 8–12 × 1015 molec. cm−2. The northwest region shows moderate concentrations, but Kashmir and northern regions of northeast show very small values of about 1–2 × 1015 molec. cm−2. Our analyses reveal significant increase in HCHO over India in all seasons, with the highest trends during March–May, about 0.3–0.5 × 1015 molec. cm−2 yr−1; suggesting the spread of pollution even to rural regions. Many ports and mining areas exhibit high positive HCHO trends, which also show new source regions and transport pathways of pollution. Furthermore, the analyses for the COVID-19 lockdown period expose significant contributions from sources other than anthropogenic origin (e.g. biogenic and pyrogenic). Therefore, this study indicates the need of new policy interventions for controlling Volatile Organic Compound (VOC) pollution in rural and urban India, and at the international seaports of Indian Ocean.
Atmospheric carbon dioxide (CO2) is an important greenhouse gas (GHG) due to its high contribution to global warming. The CO2 concentrations have increased significantly across the world after the ...industrialization. The anthropogenic provenance to the concentration of CO2 needs immediate mitigative interventions. India is a global agricultural powerhouse and significantly contributing to the global CO2 levels. Here, we present the changes in CO2 concentrations between 2009 and 2020 in India with respect to agricultural activities. We also propose steps to reduce yield scaled soil emissions through agricultural management. The CO2 concentrations in India show a steady increase of about 2.42 ppm/year from 2009 to 2020. The Central India (CEI), Hilly (HIL) and Indo-Gangetic Plain (IGP) show a relatively higher increase of about 2.43 ppm/year during the period. The highest CO2 concentration is observed during zaid (March to May) season, whereas the lowest CO2 concentration is observed during kharif (June to September) season. Anthropogenic activities such as the high use of fossil fuels and biomass burning are the two factors that significantly affect concentrations and temporal trends of CO2 in India. A pilot-scale agricultural nutrient management experiment suggests that stable carbon alternatives like biochar can reduce soil CO2 emissions without losing grain yield in paddy. Therefore, our analyses provide a better understanding of the spatio-temporal variations of CO2 over India during agricultural seasons in relation to biomass burning, vegetation and anthropogenic activities. Furthermore, it suggests a policy implication for enforcing sustainable measures to reduce CO2 emissions from agricultural activities in India.
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•Seasonal agricultural activities significantly alter atmospheric CO2 over India.•Low vegetation cover and high temperature conditions enhance CO2 emissions.•Agriculture-based anthropogenic activities drive temporal variability in CO2.•Stable carbon amendments may improve crop yield while reducing soil emissions.
Stratospheric ozone is a trace gas of great importance as it filters harmful ultraviolet radiations reaching the earth surface. Since ozone influences temperature and dynamics of the stratosphere, it ...is also a climate-relevant gas by modifyimg the tropospheric temperature. Significant changes in the stratospheric ozone are, therefore, a concern for human health and climate. India has a dedicated polar research programme with two stations in Antarctica; Maitri (70.4° S, 11.4° E, since 1989) and Bharati (69.2° S, 76.2° E, since 2012). Semi-regular measurements of total column ozone (TCO) are carried out to monitor the changes in the ozone layer there. Here, we use the available TCO measurements from Maitri in the winters of 1999–2003 and 2006, to estimate the chemical ozone depletion for the first time there. We estimate the largest ozone loss (59% or 180 DU) in 2006, and smallest in 2002 and 1999 (44% or 160 DU) among the winters; consistent with the meteorology, as the winter 2006 was the coldest and 2002 was the warmest with the first-ever major sudden stratospheric warming over Antarctica. The Maitri ozone loss analysis is found to be representative for the whole Antarctica as assessed from the comparisons with the average TCO from all Antarctic stations and satellite overpass TCO observations. The study, henceforth, demonstrates the value and significance of continuous monitoring of the ozone hole at Maitri to assist the policy decisions such as the Montreal Protocol and its amendments and adjustments.
•First-time analysis of chemical ozone loss at Maitri station in Antarctica.•Loss amounts to 170 DU or 40–50%, as for the Antarctic vortex average.•Largest loss in 2006 and smallest in 2002 in agreement with meteorology.•Maitri measurements are representative of the Antarctic vortex measurements.
Agricultural practices contribute to greenhouse gas (GHG) emissions; therefore, it is essential to modify the production technologies. We analyzed decadal variation in CO2 and CH4 over a major rice ...cultivating area in subtropical India using GOSAT satellite data, which shows a sturdy increase. Furthermore, we carried out long-term field experiments with different nutrients management in the research farm to validate CERES–Rice (Crop Environment Resource Synthesis) and DNDC (De-nitrification and Decomposition model) models. The variations in Global warming potential per kg rice grain production over 90 years (2005–2095) are also projected. This study used a simulation technique to predict the rice yield using CERES–Rice and GWP using the DNDC model for three varied nutrient management treatments: chemical fertilizer (CF) at full (100%) recommended level (CF100), organic fertilizer using vermicompost at full recommendation (VC100), and integration of organic and chemical fertilizer (VC50 + CF50). The CF100 treatment showed the highest rate of increase in GWP as 0.014 and 0.021 kg CO2eq kg-grain season−1 in RCP 4.5 and 8.5 scenarios, respectively. Integrating organic fertilizers with chemical fertilizers may give a nearly similar yield in later decades of the century in both RCP 4.5 and 8.5 climate scenarios with substantial reductions (77% in RCP 4.5 and 66% in RCP 8.5) in the rate of change in GWP as compared to sole chemical fertilizer application. This study recommends integrated nutrient management using organic fertilizers as a feasible way to limit the GHG emission from rice fields and minimize global warming in future climate scenarios.
•Increasing trend of CH4 and CO2 over central rice areas in subtropical India.•Simulation analysis using DSSAT and DNDC model evaluated mitigation options.•Application of chemical fertilizer to upland rice increased GHG emission.•A decreasing trend in GWP for rice production when organic fertilizers are included.•INM options matched to chemical fertilizer for rice yield in the later decades of the century.
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